Floatation of sheet materials



D United States Patent n 3,549,070

[ 1 Inventors 1 Frost {56] References Cited PD 9 Roy E. Downham; Jack F.Eckelaert, UNITED STATES PATENTS New, wk 3,198,499 8/1965 Stanley302/29X [21] Appl 802,923 3,231,165 1/1966 Wallin et a1 302/29X Feb.Patented Dec. 22, VIIS [73] Assignee TEC Systems, hm 3,385,490 5/1968Malmgren et al 302/29X Neenah. Wis. Primary Examiner-Allen N. Knowles acorporation of Wisconsin Anomey- Lieber & Nilles [54] FLOATATION 0FSHEET MATERIALS Claims, Drawing Figs.

[52] U.S.Ci. 226/97, ABSTRACT: Apparatus for use in floating sheetmaterials in 302/29 the nature of continuous strips or webs. Theimproved flota- [51 int. Cl. B6511 17/32 tion apparatus is particularlyuseful in the drying and/or curing Field of Search 226/7, 97; of sheetmaterials such as printed or coated paper, fabrics or 302/29 (inquired)metal sheets or strips.

PATENTED BEC22 I976 SHEEI 1 OF 3 BACKGROUND In typical drying apparatussuch as is presently in use in web offset printing, the sheet or web maybe subjected to the direct impingement of flame so as to rapidly heatthe web and the ink coating materials to the point of sustainedevaporation, such heating being followed by an air impingement treatmentwhich provides a means for the removal of the vaporizing ink solvents.In another typical example, the drying apparatus might consist of adevice for impinging hot air on the web to provide the sole means forheating, vaporizing and ventilating the printed or coated surfaces.

In either case, it is necessary that all contact with the wettedsurfaces be avoided until the ink or other coating has been dried, andin the past, this has been extremely difficult if not impossible toaccomplish, particularly since it is customary to print the web materialon both sides at the same time.

When it is desired to dry both sides of a web simultaneously utilizingair impingement for ventilation or heating, the air nozzles must be sodesigned as to prevent and/or avoid contact with the wetted surfaces.Also, every precaution must be taken to avoid or eliminate possiblevibration or fluttering of the printed or coated web since suchfluttering will frequently force the wetted material into contact withone or more of the air nozzles, and any such contact with the web, eventhough only momentary, can cause severe smearing and consequent need forrejection of the coated material due to the rapidity of advancement ofthe web through the drying zone. In addition, such nozzle contact withthe printed or coated surface can and sometimes does cause nozzleplugging, thereby necessitating shutdown of equipment for cleaningpurposes.

In prior effects to overcome these objectionable occurrences, it hasbeen the practice to either reduce the air outlet velocity at thenozzles or to increase the distance between the air nozzles and the webto minimize the possibility of web contact, or both. In either case, theair velocity is greatly reduced at the point of its impingement on theweb surface, and this decreases the efficiency of the dryer veryundesirably. In such cases, it becomes necessary to compensate for theloss of efficiency by increasing the length and, consequently, the costof the dryer.

SUMMARY It is therefore an important object of the present invention toprovide an improved apparatus for web positioning and floatation,particularly for drying purposes, which obviates the aforesaidobjections and disadvantages of prior devices of this general type.

Another object of this invention is to provide a novel and improved webpositioning and floatation apparatus which is extremely flexible in itsadaptations, highly efficient in operation, and which pennits the use ofoptimum impingement velocities without need for utilizing auxiliarydevices for aiding in the positioning of the web as it is being treatedor worked upon.

A further object of the invention is to provide an improved webfloatation device particularly adaptable for drying purposes which has aunique and improved air nozzle arrangement in which the nozzles areprotected from plugging in the event of web-to-nozzle contact.

Still another object of this invention is to provide an improved web orsheet drying apparatus especially adapted for the effective handling ofsheet materials having both sides wetted and wherein the air impingementnozzles are positi'oned with a greater than normal web-tomozzleclearance without any appreciable loss in impingement velocity.

An additional object of the present invention is to provide an improvedfloatation and positioning apparatus which is devoid of criticalclearance requirements, which will handle all types of sheet materialswith a high degree of efficiency, which is extremely effective in thefree suspension of the web without flutter or vibration, and whichpermits maximum air impingement velocity.

These and other objects and advantages of the invention will becomeapparent from the following detailed description.

THE DRAWINGS A clear conception of the construction and mode ofoperation of a typical floatation apparatus for web drying purposes maybe had by referring to the drawings accompanying and forming a part ofthis specification wherein like reference characters designate the sameor similar parts in the several views.

FIG. I is a removed sectional view of a typical floatation andpositioning device showing the impingement zone of op posed jets;

FIG. 2 is a similar removed sectional view of a modification of the FIG.I device also showing the impingement zone of opposed jets;

FIG. 3 is a removed sectional view of a positioning device according tothis invention and showing a balanced Coanda jet flowing into freespace;

FIG. 4 is a removed sectional view of an identical positioning deviceembodying the invention but showing unbalanced Coandajet flow into freespace;

FIGS. 5, 5A, 58, SC and 5D are removed sectional views of the improvedpositioning device of FIG. 3 showing air flows when a Coanda jet iscaused to impinge on an impervious material at variousmaterial-to-Coanda surface distances;

FIG. 6 is a sectional view of two identical positioning devicesembodying the improvements and showing Coanda jet flow while positioninga web between nozzles;

FIG. 7 is a sectional view of two dissimilar positioning devices, bothof which embody the invention, and showing the Coanda jet flow whilepositioning a web between the devices;

FIG. 8 is a sectional view of two dissimilar positioning devices bothembodying the invention and each having a center zone air supply;

FIG. 9 is another removed sectional view of two dissimilar positioningdevices as in FIG. 8 but each having an inadequate center zone airsupply;

FIG. 10 is still another removed sectional view of two dissimilarpositioning devices as in FIG. 8 but each having an excessive centerzone air supply;

FIG. 11 is a cross section of a typical Coanda plate;

FIGS. l2, l3, l4, and 15 are plan views of Coanda plates showing a fewof the possible orifice designs which may be used to create a centerzone air supply;

FIG. 16 is a schematic cross section of a typical floatation dryerassembly embodying the present invention and using Coandanozzles;

FIG. 17 is a removed section view of a suggested variation for thedesign of a Coanda positioning device; and

FIGS. l8, 19, 20, and 21 are removed section views of other suggestedvariations for the design of a Coanda positioning device.

DETAILED DESCRIPTION In the description of this invention, anunderstanding of the Coanda effect and of the Coanda jet flows isassumed. However, the most important aspects of the Coanda effect arebriefly described below.

First, when a gas or fluid flows along a solid surface, it tends tofollow that surface contour within defined limits.

Second, Coanda nozzles have a great ability to efliciently entrain airfrom the surrounding atmosphere, and unlike a conventional nouledischarging directly to atmosphere, a Coanda nozzle, with its protectivesurface on one side, is capable of being projected greater distanceswithout appreciable loss in velocity and momentum.

The jet from a conventional nozzle discharging directly to atmosphereinduces secondary flow partially due to the low pressure area near itsvena contracts, but the greatest amount of secondary flow is broughtabout by the collision of the high speed air molecules with the slower(or stationary) molecules of the surrounding atmosphere.

A conventional nozzle means can be defined by exacting boundaries as inFIGS. I and 2 wherein there is a definite and finite cutoff point;beyond which the air jet escaping to the surrounding atmosphere is nolonger restrained and is not protected from exterior influences.

A Coanda nozzle means can be defined by exacting boundaries, even thoughit requires a surface on only one side of a moving air jet, as shown inFIGS. 3 and 4. If the orifices 3 and 4 are large enough, and the energywithin the plenum l is great enough, the distance that the Coanda jetstream 5 will travel along the Coanda surface 6 can be many feet inlength. In the smaller dimensions of this invention, the air energylevel within the plenum I will always be of adequate measure to sustainfull Coanda jet flow across the maximum widths of ap paratus, as shownin FIG. 4, whenever conditions so permit.

Referring to FIG. 3, an air jet discharging from a Coanda orifice 3 or4, and following along a Coanda surface 6, creates a zone ofsubstantially reduced pressure immediately adjacent to the Coandasurface 6. It is this reduced pressure which causes the jet to adhere tothe Coanda surface 6.

In a conventional nozzle discharging to atmosphere as in FIGS. I and 2,the outlet velocity of the medium being moved is a direct function ofthe square root of the pressure different (AP) between the pressureinside the plenum walls 1 (P,) and the atmospheric pressure (P,,). Themaximum discharge velocity that can be obtained can be expressed by theequation:

Velocity (P, P Y C where C is a constant of the particular medium andenvironment. Since in a Coanda nozzle there is a zone of substantiallyreduced pressure (P immediately adjacent to the Coanda surface 6, whereP is less than P the velocity of that portion of the Coanda nozzlenearest the Coanda surface 6 may be expressed by the equation:

Velocity= (P P C' where C is as above and the quantity (P P A is greaterthan (P, (P, because P P,,. Since the velocity of part of a Coandanozzle is higher than any velocity obtainable from a conventionalnozzle, the average velocity of a Coanda nozzle is always higher at anygiven distance from an orifice, than the velocity of the jet streamescaping from a conventional nozzle at this same distance. In addition,the Coanda nozzle will create about itself, on its unbound side, anorderly and efficient air induction field 7 which will permit the nozzlestream to gather in surrounding air stream molecules with a minimum ofcollisions and total energy loss, far superior to the observed energylosses of conventional nozzle air streams.

In the field of high velocity air drying the advantages of a Coandanozzle system of the present invention over that of a conventionalnozzle system make it possible to design dryers with greater web tonozzle clearances without having to increase air quantities orvelocities (both a measure of power input) to prevent a loss inimpingement velocity. Also, the orderly method of outside airentrainment, as compared to the conventional method of molecularcollision now makes it possible to have high impingement velocitieswithout particular regard to web flutter or nozzle to web clearances.

All disclosures of this invention will assume the fluid to be air, andthe web material to be paper or any related flexible material. However,the application of this invention to other fluids and materials willbecome obvious. An adequate method of furnishing an unlimited supply ofair is also assumed. It is also assumed, for simplicity, that alldevices shown are endless in length, thereby eliminating anyconsideration otherwise necessary to take into account spent air flowstrans verse to the direction of web travel. In practice, transverse aircan be eliminated by providing air tight end seals at the ends of eachopposing pair of Coanda positioning devices. See FIG. 6. It is alsoassumed that the Coanda orifice openings are essentially continuousslots.

In FIGS. 3 and 4, a plenum housing 1, contains air at elevated pressure,forcing it out of the essentially endless and equal sized orificeopenings 3 and 4 formed by the mechanical spacing of the Coanda plate 2with the turned edges of housing 1. For each orifice size, there is aminimum radius R below which the air will not follow the Coanda plate 2,but will be projected in a straight path just as in a conventionalnozzle. The air from orifice openings 3 and 4 follow the Coanda plate 2around the radius R until they collide at the centerline forming acenterline main jet 8. The subatmospheric pressure formed on theexterior surface 6 of the Coanda plate 2, confines the air stream to theexterior surface 6, and, normal to the Coanda phenomenon, largequantities of surrounding air 7 are entrained into the Coanda air stream5. The main jet 8 contains all of the orifice air, 3 an 4, plus allentrained air 7.

If during balanced Coanda flow, orifice 4 is momentarily blocked, theair flow pattern will change as shown in FIG. 4. With orifice opening 4blocked, an imbalance occurs and the flow from orifice opening 3 remainson the Coanda surface 6 until it collides with the flow from orificeopening 4, forming a main jet 8 which will project upwards from thehorizontal, at some angle dependent upon the length of path traveled bythe air from opening 3, and the radius R. As in the case of FIG. 3, themain jet 8 contains all the air from orifices 3 and 4, plus allentrained air 7. It is significant to note that this new condition isstable and will remain so until orifice 3 is momentarily plugged. Iforifice 3 is plugged, a new stable flow condition will exist with allfiows reversed and opposite to that shown in FIG. 4.

Flow can be returned to the condition of FIG. 3 by momentarily blockingand opening both orifices 3 and 4 at the same time. Once a Coanda pathhas been established around the correct radius R it is a stablecondition and requires consid erable force to dislodge it. Orificeopening 3 can be somewhat different in size from orifice opening 4 andthe conditions as described above will still essentially prevail. Thisphenomenon is of significant value in the practical application of thisdevice in that it is not necessary to maintain closely held tolerancesin the construction of orifice openings 3 and 4. When conventionalnozzles are used to form zones of opposing force areas, as in FIGS. Iand 2, the orifice openings must be carefully matched or a permanent andirreversible imbalance will exist.

FIGS. 5, 5A, 5B, and 5C show a properly proportioned Coanda deviceessentially as described for FIG. 3, and the approximate air streamswhich exist when an impervious material 9 approaches the Coanda deviceof FIG. 3.

In FIG. 5, the impervious material 9, hereafter called the web, is at adistance X from the Coanda nozzle surface 6. The air from orificesopenings 3 and 4 plus the entrained air 7 combine to form a main jet 8.At a distance X the solid jet stream 8 impinges on the web 9 to form apressure or force zone approximately X in width. Since the distance X islarge, adequate space is available to provide for escape of the spentmain jet 8 after it impinges on the web 9. Also because of the greatdistance X the main jet 8 will have had time to form into a jet streamnot unlike that of a conventional nozzle and will have slowed downconsiderably but because of the large quantities of entrained air 7, thetotal momentum of the main jet 8 will be great.

In FIG. 5A the web at a distance Y will cause the solid jet stream 8 tocreate a force zone approximately Y in width, Y being larger in widththan X. Since the web 9 is now closer to the Coanda surface 6, thevelocity of impingement on the web 9 is greater. The total force on theweb 9 has increased as a function of the width Y' (or area) times thevelocity impingement pressure.

In FIG. 5B the web at a distance Z will cause the solid jet stream 8 tocreate a force zone approximately Z in width, Z being larger in widththan Y. Typical dimensions for this device could, for example, be in therange of: overall width of plenum l, 4 inches; overall width of Coandanozzle plate 2, 3 /2 inches; radius R, 7% inch; dimension Z, as inch;width of orifice openings 3 and 4, .05 inch; and width of force zone Z,3

inches. It is of significance to note here that as the clearance betweenthe web 9 and the Coanda surface 6 decreases from Y to 2 that all of theair streams from orifice openings 3 and 4 no longer collide in theirentirety at the centerline of the device. The major portion of theCoanda jet stream 5 is forced to reverse its direction in a short arebecause of the small clearance dimension Z. Some of the energy of theCoanda jet stream is spent compressing the air within the force zone,the air thus compressed is less elastic or resilient, and therefore nowable to repel the thrust of the major portion of the Coanda jet stream.An extremely small, but significant part of the Coanda jet stream 5'remains adhered to the Coanda surface 6 and penetrates the force zone,thus providing a small but constant movement of air into the force zone.

In FIG. 5C the web 9 of FIG. 5B has been inclined at some angle arelative to the horizontal portion of the Coanda surface 6. Previousexplanations have assumed the web 9 to be parallel to the horizontalportion of the Coanda surface 6. To accomplish this in practicalapplications, the web 9 would have to be absolutely rigid. In practicalapplications where the web material is of a flexible nature such aspaper, plastic film, cloth, or light gage metals, any ripple, vibration,flutter, or even minor tension variations could create a momentary setof conditions similar to those shown in FIG. 5C. With the web atposition 9', rotated through some angle a, about a point on thecenterline a distance Z from the horizontal portion of the Coandasurface 6, the flow of air to the left side is more restricted than inFIG. 5B, and the flow of air to the right side is less restricted thanin FIG. 58. Since the air on the left side of the force zone is beingcompressed more than the air on the right side of the force zone due tothe higher impingement velocity on the left, more air will escape fromthe right side of the Coanda surface than from the left side. At thisinstant in time, Coanda surface flow from orifice opening 3 increasesimmediately, combines with the Coanda surface flow from orifice opening4 and escapes to the right as shown by the jet stream arrows of FIG. 5C.

In general, flow conditions are similar to those described for theCoanda nozzle of FIG. 4, with the main jet stream 8 discharging to theright. The force zone will be of width 2', now off-center and to theleft as shown. At all times, the reactions of a Coanda nozzle meansinvolve or result in a dynamic cushion of air being formed between theweb 9 and the Coanda surface 6. If the web 9 of FIG. 5C is inclinedthrough an angle a downward to the right, all conditions will be asdescribed above, but to the opposite sides. The direction of flows wouldbe changed instantly with every movement of web 9. Laboratory tests haveproven that an angle a of 2 and less will cause instant mass flowchanges as described above.

In recalling the described events of FIGS. 5 through 5C, it is notedthat as the Coanda device is placed closer to a web 9, the higher thecompression of the air in the width of the force zone, and the greaterwill be impingement velocity on the web 9. It is significant to notethat with the web 9 positioned as in FIG. 513, that a large portion ofthe Coanda air streams 5 remains on the Coanda surface 6 until slightlypast the point of tangency between the radius R and the horizontal planeof the Coanda surface 6, then makes a full I80 reversal in direction,without a definite or sharply defined zone of high velocity airimpingement directly on the web 9.

To get direct nozzle jet impingement it is necessary to position theCoanda surface 6 close enough to the web 9 so that the resultantincrease in air compression and size of the force zone It) will be greatenough to prevent the Coanda jet stream from traveling to the point oftangency between the radius R and the horizontal plane of the Coandasurface 6, as shown in FIG. 50. The largest portion of the Coanda airstream 5 will then be stripped from the Coanda surface 6 and caused toimpinge directly on the web 9 with substantial force, such force being adirect function of the air static pressure contained within the plenumwalls I. Typically, good impingement can be obtained using the generaldimensions as described above in combination with a web to Coandasurface clearance of /sinch or less. In some industrial applications,however, a clearance dimension of 56inch is impractical.

With two opposing Coanda devices positioned as shown in FIG. 6, at someclearance dimension from the web 9 to avoid direct impingement from theCoanda air streams 5, the web 9 will be automatically and rapidlypositioned at the point of force balance between the two devices. If theweb 9 moves away from the upper Coanda device, the area and total forceof the high pressure force zone 10 will decrease. As the web 9 movestoward the bottom Coanda device, the high pressure zone 10 andconsequently the total force beneath the web 9 increases. The totalforce differential existing on each side of the web 9 forces the webtoward the weaker force field thereby increasing its value until perfectbalance is obtained.

In a machine employing the Coanda devices, if web flutter, or highamplitude angular movements are caused by an outside force, conditionsas described for FIG. 5C can and will exist. However, with opposedCoanda devices, the explanation of FIG. 5C still holds true, since asdescribed above for FIG. 6, counteracting and opposite force fields willbe set up to retrieve and maintain the web in a plane parallel to thehorizontal portion of the Coanda surface 6. Whenever web-to Coanda plateclearances occur that are too great to maintain Coanda air stream 5separation, the main jet 8 reforms instantly as in FIGS. 5 and 5A andthis single but solid air jet drives the web 9 toward its centered,balanced-force position. At all times, whenever the web 9 is a distanceof A inch or more away from the Coanda surface 6, there is a solid,dynamic cushion of air preventing the web 9 from making contact with theCoanda surface 6.

FIGS. 1 and 2 show typical positioning devices in use today whereinconventional nozzles are used in an attempt to form static air cushionsby angling two opposing air jets towards each other. In this designthere are always maximum clearance limitations. If the web a-a ispermitted to float or drift to a position where the web to nozzleclearance D is great enough to permit nozzle convergence, a zone ofextremely high turbulence is created which can cause severe web flutter.Obviously in practical drying applications such an effect would bedetrimental to the end product if such flutter were to cause smearing ornozzle plugging. In the design of high velocity dryers usingconventional nozzles, it is necessary to operate position ing devices inclose proximity to the web in order to avoid convergence and also tomaintain a static pressure pocket with enough strength to position theweb when it is being acted upon by outside forces tending to cause sheetflutters and vibrations.

Conventional positioning devices now in use in high velocity drying aregenerally limited to a maximum web-todevice clearance in the range of isto /4 inches. The Coanda device described herein will position webswithout web turbulence, at web-to-Coanda plate clearances in excess ofone inch, using the same air power input as required by conventionaldevices.

Because the Coanda air stream 5 is essentially a nozzle means, and theCoanda surface 6 is the most distant part of the nozzle means from theweb 9, it can be said that the Coanda surface provides the nozzle meansfor instant and accurate automatic positioning of a nozzle jet such thatthe discharge of the jet will always provide either a moving air film 5,or a dynamic pressure zone 10 between the surface being positioned andthe Coanda plate, and always one or the other, dependent upon whether ornot the web 9 to Coanda surface 6 clearance is maximal or minimal.

The apparatus of FIG. 6 discloses an improved positioning device, ofparticular value in positioning heavy somewhat rigid materials such aspaper board, sheet steel or heavy films. Lighter weight material such asmagazine paper stock is extremely flexible and rapidly responsive tovariations in tension control while being processed, that is, printed,coated, etc. If, during processing, tension is momentarily minimized andsome web stack is permitted, the flexible material may be drawn into thereturn air passages 20 as shown in FIGv 16. Such movement wouldgenerally cause smearing of the coating or ink, and very possibly causethe material to fracture or tear necessitating loss of production timeto rethread the material through the coating or printing machine and ifconventional nozzles were used, additional time loss would be requiredto clear the nozzle openings in the event they were smeared shut withcoating or ink.

FIG. 7 shows an apparatus design with the ability to cope with greatvariations in tension. The upper and lower devices are essentially aspreviously described except that the lower device is of smaller width. Asatisfactory variation would be an overall Coanda plate width of 3.5inches on the upper and 2.5 inches on the lower, using orifice openingsin the range of .050 to .070 inches. The positioning reactions andpressure force buildups will occur as described above, but now the totalforce exerted by the top Coanda device will be greater than the totalforce exerted by the bottom Coanda device. However, with all orifices 3and 4 of about the same size, in keeping with practical commercialtolerances and practices. the unit pressure 10, exerted on each side ofthe web 9 will be the same. The unit pressure 10 on the top of the web 9acts over a larger area, and where this unit pressure 10 is not opposedby a like unit pressure 10, the web 9 will be caused to deflectdownward, away from the motivating force as shown by dotted line 11. Theapproximate axis of bending will be at the intersection of the web 9with a centerline drawn from the midpoint of each opposing pair ofoffset nozzles 3 and 4.

By mounting the Coanda positioners of FIG. 7 side by side, in alternateorder as shown in FIG. 16, where 17 is a Coanda positioner with a narrowCoanda plate, and 18 is a Coanda positioner with a wide Coanda plate, itis possible to neutralize the composite resultant of all upper and lowerforce fields 10. The use of this mounting method provides the Coandasystem with the tendency to position the web with a sine wave pattern 11as shown in FIG. 16. Because these tendency forces exist,

any slack which may appear in the web being processed will immediatelybe absorbed into the sine wave pattern, thereby preventing any slack orloose portions of the web from making contact with any parts of theCoanda positioning devices.

In all positioning devices disclosed thus far it is apparent that highvelocity jet impingement does not take place under a Coanda positionerunless web to Coanda surface clearances are fairly small, approximatelya inch or less.

FIG. 8 is essentially the same device as shown in FIG. 7 except thatadditional nozzle openings 12 have been added along the centerline ofthe Coanda plate 2. Typical hole patterns suitable for this purpose areshown in FIGS. ll, 12, 13, I4, and 15. Orifice openings 12 serve atwofold purpose: firstly, they provide an additional and effectivesource of high velocity air impingement which essentially reduces thecenter to center distance between impinging jets and increases the heatand mass transfer coefficients of the apparatus close to optimum.Secondly, the noules 12 provide an air supply to the pressure zone 10thereby making it possible to maintain the high pressure required topeel the Coanda air stream from the Coanda surface 6 to obtain directjet impingement on the web 9 at greater web-to-Coanda surface distances.Sizing of the center holes 12 is critical in relation to the size of thenozzle openings 3 and 4, and to the design of the Coanda surfaceto-webclearances desired.

If the centerline air supply 12 is insufficient, no appreciable changein performance over the device of FIG. 7 is noted. FIG. 9 shows typicalair stream patterns for such a device.

FIG. 10 shows typical air stream patterns if the centerline air supply12 is too great. A great excess of air essentially duplicates conditionsas though the web 9 to Coanda surface 6 distance were very small. Airmust escape from the force zone 10 at such a rapid rate, that in sodoing, the largest portion of the Coanda nozzle air stream 5 isdeflected outward at such an angle as to prevent direct impingement onthe web 9.

It is obvious, therefore, that for each design of web to Coanda surfacedistance desired, that it is possible to select various combinations oforifice openings 3 and 4, and centerline supply air openings 12, suchthat it is possible to obtain any desired angle of impingement betweenthe Coanda nozzle air stream 5 and the web 9.

FIG. 8 shows the air streams of a balanced flow Coanda positioning anddrying device. The centerline supply orifices 12 provide the correctamount of air to provide adequate dynamic pressurization of the forcezone 10 such that portions of the Coanda air streams 5 are peeled fromthe Coanda surface 6 and caused to impinge directly on the surface ofweb 9. With the device of FIG. 8 it is possible to duplicate all of theconditions of the device of FIG. D, but at much greater clearancedistances between the web 9 and the Coanda surface 5.

FIGS. 17, l8, 19, 20, 21, and 22 show a few of the alternate methodspossible to design a Coanda positioning device using the information ofthis disclosure. Materials of construction can obviously be of anysubstance suitable to the atmosphere, that is, temperature, humidity,corrosion, etc. that the device must operate in. Other modificationswill become apparent to those skilled in the art.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:

1. Apparatus for floating sheet material in the nature of a continuousweb, comprising, means forming a linear Coanda nozzle extending in adirection transversely of web travel adjacent a surface of the web, saidnozzle being oriented with respect to the web so that the flow of gasinduced by said nozzle originates adjacent the surface of the web facingsaid nozzle and is directed over the Coanda surface longitudinally ofthe direction of travel of the web.

2. Apparatus according to claim I, wherein a pair of linear Coandanozzles are provided, said nozzles being parallel to one another andbeing spaced longitudinally of the direction of web travel.

3. Apparatus according to claim 2, wherein the nozzles are so orientedwith respect to the web that the flow of gas induced by each nozzleoriginates adjacent the surface of the web facing the respective nozzleand is directed over the Coanda surface longitudinally of the directionof travel of the web and toward the other nozzle.

4. Apparatus according to claim 2, wherein a Coanda plate spans thespace between the Coanda nozzles, and additional nozzle means are fonnedin said plate intermediate said spaced Coanda nozzles.

5. Apparatus according to claim 4, wherein the additional nozzle meanscomprises a series of spaced orifices in the plate and extending in apath transversely of web travel.

6. Apparatus according to claim 3, wherein a plurality of pairs oflongitudinally spaced Coanda nozzles are provided.

7. Apparatus according to claim 1, wherein means forming a linear Coandanozzle are provided both above and below the web.

8. Apparatus according to claim 1, wherein a pair of Coanda nozzles areprovided above the web and a pair of Coanda nozzles are provided belowthe web, all of said nozzles being parallel to one another, and thenozzles of each pair are spaced longitudinally in the direction of webtravel.

9. Apparatus according to claim 8, wherein a plurality of pairs oflongitudinally spaced Coanda nozzles are provided both above and belowthe web.

10. Apparatus according to claim 8, wherein the nozzles are so orientedwith respect to the web that the flow of gas induced by each nozzleoriginates adjacent the surface of the web facing the respective nozzleand is directed over the Coanda surface longitudinally of the directionof travel of the web and toward the adjacent nozzle.

11. Apparatus according to claim 8, wherein a Coanda plate spans thespace between each pair of Coanda nozzles, and additional nozzle meansare formed in each plate intermediate the respective pairs of Coandanozzles.

in that said apparatus includes a plenum Coanda supporting air pressure,and said linear Coanda nozzle is located adjacent one side of saidplenum. Coanda 15. The apparatus as set forth in claim 14 further characterized in that said plenum includes a coanda plate extending along thedirection of web travel, and the air from said nonle travels along saidcoanda plate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION atent No 3,549,070December 22 1970 John W. Frost et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 10, line 1, "Coamda should read for line 3, :ancel Coandal"Signed and sealed this 6th day of April 1971.

ISEAL) rttesti DWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR.

ttesting Officer Commissioner of Patents Disclaimer 3,549,070.John W.Frost, Appleton, Roy E. Downham and J ask F. Eckelaert, Neenah, Wis.FLOATATION OF SHEET MATERIALS. Patent dated Dec. 22, 1970. Disclaimerfiled Nov. 12, 1975, by the assignee TEO' Systems, Inc.

Hereby enters this disclaimer to claims 1, 2, 7, 8, 9, 10, 13, 14 and 15of said patent.

[Oficz'al Gazette January 13, 1.976.]

